文摘

Podostemaceae is the largest family of fresh water aquatic angiosperms, which exhibits many unusual morphological and reproductive features. In India, the family is represented by 11 genera and 28 species, of which ~82?% are endemic. So far, the infrageneric relationships of the Indian taxa have remained unresolved. We carried out a phylogenetic study of the Indian Podostemaceae using ITS sequence data and morphological characters. New data for the Indian species was generated and pooled with the previous ones, representing major groups of the Podostemaceae, to assess the placement and establish interrelationships of the Indian genera. The Indian Podostemaceae comprises two subfamilies: Podostemoideae and Tristichoideae. The phylogenetic analysis reveals that the Indian Podostemoideae is subdivided into two subclades; one represented by Willisia and Podostemum and the other by Zeylanidium, Hydrobryopsis, Griffithella and Polypleurum. The study suggests that the Indian species of Podostemum and Hydrobryopsis should not be merged with Zeylanidium as suggested earlier. In Tristichoideae, Indian species of Dalzellia and Indotristicha form a clade, which is sister to Tristicha. However, the analyses indicate that within the Indotristicha–Dalzellia clade, I. tirunelveliana is a sister species, with a high support to Dalzellia instead of its congener I. ramosissima. Based on morphological and molecular data, we propose the removal of I. tirunelveliana from the genus Indotristicha. Present study also provides insight into the evolution of some morphological characters in Podostemaceae.